Right heart catheterization was performed without premedication, with the patient lying supine and breathing room air. A balloon-tipped, flow-directed thermodilution 7F Swan-Ganz catheter (131HF7; Baxter Healthcare Corp; Irvine, CA) was inserted under local anesthesia into an internal jugular vein and was floated under continuous pressure-wave monitoring into a pulmonary artery to measure Ppa, pulmonary artery occluded pressure (Ppao), right atrial pressure (Pra), and cardiac output (Q). Systemic arterial pressure (Psa) was determined intermittently by an automated BP cuff. Heart rate (HR) was determined from a continuously monitored ECG lead. Pulmonary vascular pressures were measured using disposable transducers (TruWave; Baxter Healthcare Corp) connected to a bedside hemodynamic and ECG monitoring system (Sirecust 404; Siemens; Erlangen, Germany). The pressure transducers were zero-referenced at midchest, and vascular pressures were obtained at end-expiration. The static calibration was checked against a water column, and the dynamic response of the catheter-manometer system was checked using the “fast flush” test. Cardiac output was measured using the thermodilution technique as a mean of at least three successive measurements (COM-2; Baxter Healthcare Corp). The pulmonary vascular pressure signals were sampled at 200 Hz using an analog/digital converter (DAS 8-PGA; Keithley-Metrabyte; Taunton, MA), and were stored and analyzed on a personal computer.
Transthoracic Doppler echocardiography was performed (SO-NOS 2000; Hewlett-Packard; Palo Alto, CA) with a 3.5-MHz probe during catheterization with the patient in a dorsal or lateral supine position. Pulsed-Doppler velocity was recorded in the RV outflow tract using the short-axis parasternal view, as previously described. Sampling frequency and gain setting were optimized to obtain the best flow-velocity envelope. In our center, the interobserver variability for pulmonary arterial flow acceleration time and the velocity-time integral is < 5%.